Denver ? Convicted 9-11 conspirator Zacarias Moussaoui began serving his life sentence at the nation’s most secure prison on Saturday after U.S. marshals flew him overnight to southern Colorado from Virginia.

Marshals brought Moussaoui, prisoner 51427-054, before dawn to the Supermax federal prison, where he will spend 23 hours a day in his cell and have little to no contact with the other notorious criminals.

The $60 million Supermax, formally called Administrative Maximum, was built in 1995 in a town of 3,600 people. The triangular, two-story prison was designed for inmates once held at the U.S. Penitentiary in Marion, Ill., which had replaced Alcatraz when it closed in 1963.

Among the inmates at the prison are Ramzi Yousef, Eric Rudolph, Ted Kaczynski and Terry Nichols. Also there is Richard Reid, the would-be shoe bomber Moussaoui said was to help him fly a fifth plane into the White House. The Bureau of Prisons said the Supermax currently houses 398 “of the nation’s most violent, disruptive and escape prone inmates.”